I did NOT do "disavow" because I hadn't built any links, and I am seeing indications of some small recovery today.
--I'm back in the top 30 positions for a number of long tail phrases that had fallen below that level after Penguin.
--After Penguin, some of my pages fell to between about 300-800. Now those pages are in the 50-150 range.
--And the page hit the hardest by Penguin is back in my sitelinks. I don't know how much to read into that, since I'm not sure if sitelinks mean much anymore, but it's definitely a change and it just happened today.
These changes don't seem to be improving my overall traffic volume from Google. I'm just sharing them in case they provide any clue to how Penguin works or what it's looking for.